Experimental investigation of the processes determining x-ray emission intensities from charge-exchange collisions

Greenwood, J. B.; Williams, Ian D.; Smith, S. J.; Chutjian, A.

doi:10.1103/physreva.63.062707

Cited by 121 publications

(116 citation statements)

References 46 publications

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“…While some important emission lines like O 6+ and O 7+ have been reasonably well characterized, many others that contribute to the emissions with energies < 500 eV that are relevant to imaging solar wind interactions with the planetary objects are not (see Smith et al 2014, for a discussion of alternative methods). Beiersdorfer et al (1999Beiersdorfer et al ( , 2000Beiersdorfer et al ( , 2001Beiersdorfer et al ( , 2003, Wargelin et al (2008), Greenwood et al (2001), Mawhorter et al (2007), and Betancourt-Martinez et al (2014) present some relatively recent experimental measurements of X-ray emissions generated by charge exchange. (See also the review within Krasnopolsky et al 2004.)…”

Section: Experimental Measurements Of Charge-exchange Cross Sectionsmentioning

confidence: 99%

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

et al. 2018

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Both heliophysics and planetary physics seek to understand the complex nature of the solar wind's interaction with solar system obstacles like Earth's magnetosphere, the ionospheres of Venus and Mars, and comets. Studies with this objective are frequently conducted with the help of single or multipoint in situ electromagnetic field and particle observations, guided by the predictions of both local and global numerical simulations, and placed in con- text by observations from far and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or transient magnetic reconnection, local or global magnetic reconnection, ion pick-up, or the KelvinHelmholtz instability) generates diagnostic plasma density structures. The significance of each mechanism to the overall interaction (as measured in terms of atmospheric/ionospheric loss at comets, Venus, and Mars or global magnetospheric/ionospheric convection at Earth) remains to be determined but can be evaluated on the basis of how often the density signatures that it generates are observed as a function of solar wind conditions. This paper reviews efforts to image the diagnostic plasma density structures in the soft (low energy, 0.1-2.0 keV) X-rays produced when high charge state solar wind ions exchange electrons with the exospheric neutrals surrounding solar system obstacles. The introduction notes that theory, local, and global simulations predict the characteristics of plasma boundaries such the bow shock and magnetopause (including location, density gradient, and motion) and regions such as the magnetosheath (including density and width) as a function of location, solar wind conditions, and the particular mechanism operating. In situ measurements confirm the existence of time-and spatial-dependent plasma density structures like the bow shock, magnetosheath, and magnetopause/ionopause at Venus, Mars, comets, and the Earth. However, in situ measurements rarely suffice to determine the global extent of these density structures or their global variation as a function of solar wind conditions, except in the form of empirical studies based on observations from many different times and solar wind conditions. Remote sensing observations provide global information about auroral ovals (FUV and hard X-ray), the terrestrial plasmasphere (EUV), and the terrestrial ring current (ENA). ENA instruments with low energy thresholds (∼ 1 keV) have recently been used to obtain important information concerning the magnetosheaths of Venus, Mars, and the Earth. Recent technological developments make these magnetosheaths valuable potential targets for high-cadence wide-field-of-view soft X-ray imagers.Section 2 describes proposed dayside interaction mechanisms, including reconnection, the Kelvin-Helmholtz instability, and other processes in greater detail with an emphasis on the plasma density structures that they generate. It focuses upon the questions that remain as yet unanswered, such as the significanc...

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Section: Experimental Measurements Of Charge-exchange Cross Sectionsmentioning

confidence: 99%

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

et al. 2018

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“…Although multielectron neutral targets might be important for some environments (e.g., comets) where the channels of multi-electron capture do exist (e.g., Bodewits et al 2006), the data available on such reactions are much less complete than those for single electron capture. As shown in the experimental results of, for example, Greenwood et al (2001), single capture can provide a first-order approximation to multi-electron reactions. Secondly, as a related issue, we assume that the CX with atomic hydrogen is a reasonable representative of the real case, in terms of the cross section dependences on ion velocity and captured electron state (see details in Sect.…”

Section: Assumptionsmentioning

confidence: 92%

Plasma code for astrophysical charge exchange emission at X-ray wavelengths

Kaastra

Raassen

2016

A&A

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Charge exchange X-ray emission provides unique insight into the interactions between cold and hot astrophysical plasmas. Besides its own profound science, this emission is also technically crucial to all observations in the X-ray band, since charge exchange with the solar wind often contributes a significant foreground component that contaminates the signal of interest. By approximating the cross sections resolved to n and l atomic subshells and carrying out complete radiative cascade calculation, we have created a new spectral code to evaluate the charge exchange emission in the X-ray band. Compared to collisional thermal emission, charge exchange radiation exhibits enhanced lines from large-n shells to the ground, as well as large forbidden-to-resonance ratios of triplet transitions. Our new model successfully reproduces an observed high-quality spectrum of comet C/2000 WM1 (LINEAR), which emits purely by charge exchange between solar wind ions and cometary neutrals. It demonstrates that a proper charge exchange model will allow us to probe the ion properties remotely, including charge state, dynamics, and composition, at the interface between the cold and hot plasmas.

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“…Experimental measurements continue to be important for quantitative analysis of charge exchange spectra (e.g., Beiersdorfer et al 2000;Greenwood et al 2000;Otranto and Olson 2011). Dennerl (2010) provides a good review of this field.…”

Section: Planetary Systems and Star Formationmentioning

confidence: 99%

The impact of recent advances in laboratory astrophysics on our understanding of the cosmos

et al. 2012

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Abstract. An emerging theme in modern astrophysics is the connection between astronomical observations and the underlying physical phenomena that drive our cosmos. Both the mechanisms responsible for the observed astrophysical phenomena and the tools used to probe such phenomena -the radiation and particle spectra we observe -have their roots in atomic, molecular, condensed matter, plasma, nuclear and particle physics. Chemistry is implicitly included in both molecular and condensed matter physics. This connection is the theme of the present report, which provides a broad, though non-exhaustive, overview of progress in our understanding of the cosmos resulting from recent theoretical and experimental advances in what is commonly called laboratory astrophysics. This work, carried out by a diverse community of laboratory astrophysicists, is increasingly important as astrophysics transitions into an era of precise measurement and high fidelity modeling.

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Experimental investigation of the processes determining x-ray emission intensities from charge-exchange collisions

Cited by 121 publications

References 46 publications

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

Plasma code for astrophysical charge exchange emission at X-ray wavelengths

The impact of recent advances in laboratory astrophysics on our understanding of the cosmos

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